U.S. patent number 10,090,189 [Application Number 14/541,488] was granted by the patent office on 2018-10-02 for substrate cleaning apparatus comprising a second jet nozzle surrounding a first jet nozzle.
This patent grant is currently assigned to EBARA CORPORATION. The grantee listed for this patent is EBARA CORPORATION. Invention is credited to Tomoatsu Ishibashi.
United States Patent |
10,090,189 |
Ishibashi |
October 2, 2018 |
**Please see images for:
( Certificate of Correction ) ** |
Substrate cleaning apparatus comprising a second jet nozzle
surrounding a first jet nozzle
Abstract
A substrate cleaning apparatus capable of removing particles
that exist in minute recesses formed on a substrate surface is
disclosed. The substrate cleaning apparatus includes a substrate
holder configured to hold a substrate; and a two-fluid nozzle
configured to deliver a two-fluid jet onto a surface of the
substrate. The two-fluid nozzle includes a first jet nozzle
configured to emit a first two-fluid jet and a second jet nozzle
configured to emit a second two-fluid jet at a velocity higher than
a velocity of the first two-fluid jet, and the second jet nozzle
surrounds the first jet nozzle.
Inventors: |
Ishibashi; Tomoatsu (Tokyo,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
EBARA CORPORATION |
Tokyo |
N/A |
JP |
|
|
Assignee: |
EBARA CORPORATION (Tokyo,
JP)
|
Family
ID: |
53181612 |
Appl.
No.: |
14/541,488 |
Filed: |
November 14, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150144164 A1 |
May 28, 2015 |
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Foreign Application Priority Data
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Nov 19, 2013 [JP] |
|
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2013-239040 |
Nov 19, 2013 [JP] |
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2013-239041 |
Nov 22, 2013 [JP] |
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2013-241960 |
Nov 25, 2013 [JP] |
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2013-242716 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/68792 (20130101); H01L 21/67051 (20130101) |
Current International
Class: |
H01L
21/67 (20060101); H01L 21/687 (20060101); H01L
21/68 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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S50-6362 |
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S58-130532 |
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JP |
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S60-261582 |
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JP |
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S61-192379 |
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JP |
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H08-318181 |
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H10-156229 |
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11-058226 |
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2000-157939 |
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2001-053047 |
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2003-017452 |
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2003-031540 |
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2004-096023 |
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2005-288394 |
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2007-027270 |
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2007-073610 |
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2008-108829 |
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JP |
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2009-088078 |
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Apr 2009 |
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JP |
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2010-238850 |
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Oct 2010 |
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JP |
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2011-507236 |
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Mar 2011 |
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JP |
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2011-077144 |
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Apr 2011 |
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JP |
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2013-077597 |
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Apr 2013 |
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JP |
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2013-089797 |
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May 2013 |
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JP |
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2013-175496 |
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Sep 2013 |
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JP |
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2013-179341 |
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Sep 2013 |
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JP |
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2013-214737 |
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Oct 2013 |
|
JP |
|
Other References
English Translation of Japanese Office action issued in Patent
Application No. JP 2013-239040 dated Aug. 17, 2017. cited by
applicant .
English Translation of Japanese Office action issued in Patent
Application No. JP 2013-239041 dated Aug. 17, 2017. cited by
applicant .
English Translation of Japanese Office action issued in Patent
Application No. JP 2013-242716 dated Aug. 17, 2017. cited by
applicant .
Singapore Search Report issued in Singapore Patent Application No.
10201407598V dated Jul. 25, 2017. cited by applicant.
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Primary Examiner: Barr; Michael E
Assistant Examiner: Adhlakha; Rita P
Attorney, Agent or Firm: Pearne & Gordon LLP
Claims
What is claimed is:
1. A substrate cleaning apparatus comprising: a substrate holder
configured to hold a substrate; and a two-fluid nozzle configured
to deliver fluid onto a surface of the substrate, wherein the
two-fluid nozzle includes: a liquid container having a liquid
chamber and a chamber inlet in communication with the liquid
chamber, a first jet nozzle in communication with the liquid
chamber and having a first gas inlet, the first jet nozzle being
configured to emit a first two-fluid jet, the first two-fluid jet
comprising a gas from the first gas inlet and a liquid from the
liquid container, and a second jet nozzle in communication with the
liquid chamber and having a second gas inlet, the second jet nozzle
being configured to emit a second two-fluid jet at a velocity
higher than a velocity of the first two-fluid jet, the second
two-fluid jet comprising a gas from the second gas inlet and the
liquid from the liquid container the second jet nozzle surrounding
the first jet nozzle.
2. The substrate cleaning apparatus according to claim 1, wherein
the velocity of the second two-fluid jet is not less than a speed
of sound.
3. The substrate cleaning apparatus according to claim 1, further
comprising: a nozzle moving mechanism configured to move the
two-fluid nozzle in a radial direction of the substrate.
4. The substrate cleaning apparatus according to claim 1, further
comprising: a distance adjuster configured to change a distance
between the two-fluid nozzle and the surface of the substrate.
5. The substrate cleaning apparatus according to claim 1, further
comprising: a third jet nozzle disposed inside the first jet nozzle
and configured to emit a third two-fluid jet at a velocity higher
than the velocity of the first two-fluid jet.
6. The substrate cleaning apparatus according to claim 5, wherein
the velocity of the third two-fluid jet is not less than a speed of
sound.
7. The substrate processing apparatus according to claim 1, further
comprising a polishing unit configured to polish the substrate.
8. The substrate processing apparatus according to claim 1, further
comprising at least one oscillator that is to come in contact with
the substrate to vibrate the substrate.
9. The substrate cleaning apparatus according to claim 8, wherein
the oscillator is configured to rotate together with the substrate
while vibrating the substrate.
10. The substrate cleaning apparatus according to claim 8, wherein
the oscillator includes a piezoelectric element, and a contact
member that is mounted to the piezoelectric element and is to come
in contact with the substrate.
11. The substrate cleaning apparatus according to claim 8, wherein
the oscillator is configured to vibrate the substrate in a
direction perpendicular to the surface of the substrate.
12. The substrate cleaning apparatus according to claim 8, wherein
the oscillator is configured to vibrate the substrate in a
direction parallel to the surface of the substrate.
13. The substrate cleaning apparatus according to claim 8, wherein
the at least one oscillator comprises at least one first oscillator
configured to vibrate the substrate in a direction perpendicular to
the surface of the substrate and at least one second oscillator
configured to vibrate the substrate in a direction parallel to the
surface of the substrate.
14. The substrate cleaning apparatus according to claim 8, wherein
the at least one oscillator comprises a plurality of oscillators,
and at least two of the plurality of oscillators are configured to
vibrate the substrate at different frequencies and/or different
amplitudes.
15. The substrate cleaning apparatus according to claim 8, further
comprising: a cleaning-liquid nozzle configured to supply a
cleaning liquid onto a lower surface of the substrate; and an
ultrasonic transducer configured to vibrate the cleaning
liquid.
16. The substrate processing apparatus according to claim 8,
further comprising a polishing unit configured to polish the
substrate.
17. The substrate cleaning apparatus according to claim 1, wherein:
the first jet nozzle receives liquid from the liquid chamber via
first liquid inlet, and the second jet nozzle receives liquid from
the liquid chamber via a second liquid inlet.
18. The substrate cleaning apparatus according to claim 17, wherein
the first jet nozzle extends through the liquid chamber and the
first liquid inlet is in direct fluid communication with the liquid
chamber.
19. A substrate cleaning apparatus comprising: a substrate holder
configured to hold a substrate; and a two-fluid nozzle configured
to deliver fluid onto a surface of the substrate, wherein the
two-fluid nozzle includes: a liquid container having a liquid
chamber and a chamber inlet in communication with the liquid
chamber, a first jet nozzle in communication with the liquid
chamber and having a first gas inlet, the first jet nozzle being
configured to emit a two-fluid jet, the two-fluid jet comprising a
gas from the first gas inlet and a liquid from the liquid
container, and a second jet nozzle having a second gas inlet, the
second jet nozzle being configured to emit a gas jet at a velocity
higher than a velocity of the two-fluid jet, the gas jet comprising
a gas from the second gas inlet the second jet nozzle surrounding
the first jet nozzle.
20. The substrate processing apparatus according to claim 19,
further comprising a polishing unit configured to polish the
substrate.
21. The substrate cleaning apparatus according to claim 19, wherein
the first jet nozzle receives liquid from the liquid chamber via a
first liquid inlet.
22. A two-fluid nozzle for use in a substrate cleaning apparatus,
comprising: a liquid container having a liquid chamber and a
chamber inlet which are in communication with each other; a first
jet nozzle in communication with the liquid chamber and having a
first gas inlet, the first jet nozzle being configured to emit a
first two-fluid jet, the first two-fluid jet comprising a gas from
the first gas inlet and a liquid from the liquid container; and a
second jet nozzle in communication with the liquid chamber and
having a second gas inlet, the second jet nozzle being configured
to emit a second two-fluid jet, the second two-fluid jet comprising
a gas from the second gas inlet and the liquid from the liquid
containerm, and the second jet nozzle surronding the first jet
nozzle.
23. The two-fluid nozzle according to claim 22, further comprising:
a third jet nozzle disposed inside the first jet nozzle.
24. The substrate cleaning apparatus according to claim 22,
wherein: the first jet nozzle receives liquid from the liquid
chamber via a first liquid inlet, and the second jet nozzle
receives liquid from the liquid chamber via a second liquid
inlet.
25. The substrate cleaning apparatus according to claim 24, wherein
the first jet nozzle extends through the liquid chamber and the
first liquid inlet is in direct fluid communication with the liquid
chamber.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This document claims priorities to Japanese Patent Application
Number 2013-239040 filed Nov. 19, 2013, Japanese Patent Application
Number 2013-239041 filed Nov. 19, 2013, Japanese Patent Application
Number 2013-241960 filed Nov. 22, 2013 and Japanese Patent
Application Number 2013-242716 filed Nov. 25, 2013, the entire
contents of which are hereby incorporated by reference.
BACKGROUND
As semiconductor devices have been becoming finer in recent years,
various material films having different properties are formed on a
substrate, and are processed. In particular, in a damascene
interconnect forming process in which interconnect trenches formed
in a dielectric film are filled with a metal, an excessive metal is
polished away by a polishing apparatus after a metal film is
formed. Various films, such as a metal film, a barrier film, and a
dielectric film, are exposed on a wafer surface that has been
polished. Residues, such as slurry used in polishing and polishing
debris, remain on these films that are exposed on the wafer
surface. In order to remove these residues, the polished wafer is
transported to a substrate cleaning apparatus, where the wafer
surface is cleaned.
If cleaning of the wafer surface is insufficient, reliability
problems, such as poor adhesion and a current leak due to the
existence of the residues, may occur. Therefore, in manufacturing
of a semiconductor device, cleaning of the wafer has been an
important process for improving a yield of products.
As an apparatus for cleaning a substrate, there has been known a
two-fluid cleaning apparatus that supplies a two-fluid jet,
composed of a fluid mixture of a gas and a liquid, onto a surface
of a substrate to thereby clean the substrate. As shown in FIG. 42,
the two-fluid cleaning apparatus delivers the two-fluid jet from a
two-fluid nozzle 500 onto a surface of a substrate W, while the
two-fluid nozzle 500 is moved parallel to the surface of the
substrate W, to generate shock waves by a collision between the
two-fluid jet and the substrate W, thereby removing particles, such
as abrasive grains and polishing debris, which exist on the surface
of the substrate W.
However, as shown in FIG. 43, since the two-fluid jet reaches the
substrate while spreading, an incident angle .theta. of the shock
wave with respect to the substrate surface is small. As a result,
as shown in FIG. 44, the shock waves do not impinge on particles
existing in minute recesses on the substrate surface, thus failing
to remove these particles.
FIG. 45 is a schematic view showing a structure of the two-fluid
cleaning apparatus shown in FIG. 42. As shown in FIG. 45, a gas
supply line 555 for supplying a gas into a gas pocket 560 formed in
the two-fluid nozzle 500, and a liquid supply line 557 for
supplying a liquid into a mixing chamber 561 formed in the
two-fluid nozzle 500 are coupled to the two-fluid nozzle 500. The
two-fluid nozzle 500 has a gas introduction port 564 at its upper
portion, and the gas supply line 555 is coupled through this gas
introduction port 564 to the two-fluid nozzle 500.
The liquid supply line 557 extends downwardly through the gas
pocket 560 that is formed in the two-fluid nozzle 500. A liquid
outlet 557a of the liquid supply line 557 is located in the
two-fluid nozzle 500. The gas pocket 560 is located above the
liquid outlet 557a of the liquid supply line 557, and the mixing
chamber 561 is located below the liquid outlet 557a of the liquid
supply line 557. The liquid, such as pure water, is supplied
through the liquid supply line 557 into the mixing chamber 561
formed in the two-fluid nozzle 500.
The gas supply line 555 is provided with a gas supply valve 571 and
a filter 572. The gas (e.g., inert gas, such as nitrogen gas)
flowing in the gas supply line 555 passes through the gas supply
valve 571 and the filter 572 in this order and further flows
through the gas introduction port 564 into the gas pocket 560 of
the two-fluid nozzle 500. The gas supply valve 571 may be a flow
control valve (e.g., a mass flow controller), an air operated
valve, an on-off valve, or the like.
The liquid and the gas are mixed in the mixing chamber 561 to form
a high-pressure two-fluid mixture. During supplying of the gas into
the gas pocket 560, as shown in FIG. 46, the gas supply valve 571
is opened and closed with a short period (e.g., 0.1 to 1.0 second).
Therefore, the gas is intermittently supplied into the gas pocket
560, and as a result, a flow rate of the two-fluid mixture varies
periodically. A jet of the two-fluid mixture that is pulsating in
this manner is delivered onto the surface of the substrate, thereby
removing the abrasive grains and the polishing debris from the
surface of the substrate.
When the gas supply valve 571 is periodically opened and closed,
the flow rate of the two-fluid mixture formed in the mixing chamber
561 is expected to pulsate in accordance with a flow rate of the
gas as well. However, when the gas supply valve 571 is opened and
closed with a short period, an amplitude of the flow rate of the
two-fluid mixture becomes smaller than expected, as shown in FIG.
47, due to a residual pressure existing in the gas pocket 560. As a
result, a cleaning performance of the two-fluid jet is lowered.
FIG. 48 is a schematic view showing a droplet of the two-fluid
mixture. As shown in FIG. 48, the droplet, which constitutes the
two-fluid jet, typically has a size of several tens of .mu.m, while
fine particles on the substrate W have a size of at most 100 nm.
Therefore, as shown in FIG. 49, the droplet cannot enter recesses
(e.g., stepped portions of patterns and scratches) formed on the
substrate surface, and as a result, cannot remove the fine
particles existing in these recesses.
The two-fluid cleaning apparatus has an advantage that a back
contamination of the substrate W does not occur, because a cleaning
tool, such as a brush or a sponge, is not brought into contact with
the substrate W. However, it is difficult for such cleaning
apparatus using only the two-fluid jet to sufficiently remove the
particles attached to the surface of the substrate W. In
particular, the two-fluid jet cannot remove the fine particles
existing in the recesses (e.g., stepped portions of patterns and
scratches) formed on the substrate surface.
SUMMARY OF THE INVENTION
In an embodiment, there is provided a substrate cleaning apparatus
capable of removing particles that exist in minute recesses formed
on a substrate surface.
In an embodiment, there is provided a substrate cleaning apparatus
capable of supplying a two-fluid jet onto a substrate while causing
the two-fluid jet to pulsate greatly.
In an embodiment, there is provided a substrate cleaning apparatus
capable of making droplets of a two-fluid mixture smaller to
improve a substrate cleaning effect.
In an embodiment, there is provided a substrate cleaning apparatus
capable of cleaning a surface of a substrate highly efficiently
with use of a two-fluid jet.
In an embodiment, there is provided a substrate processing
apparatus incorporating such substrate cleaning apparatus.
Embodiments, which will be described below, relate to a substrate
cleaning apparatus that delivers a two-fluid jet, composed of a gas
and a liquid, onto a substrate, such as a wafer, to thereby clean
the substrate, and particularly relates to a substrate cleaning
apparatus that delivers the two-fluid jet onto a surface of a
polished substrate to thereby clean the substrate. The substrate
cleaning apparatus according to the present invention is applicable
to cleaning of not only a wafer having a diameter of 300 mm but
also a wafer having a diameter of 450 mm, and is further applicable
to a manufacturing process of a flat panel, a manufacturing process
of an image sensor, such as CMOS and CCD, a manufacturing process
of a magnetic film for MRAM, and other processes.
In an embodiment, there is provided a substrate cleaning apparatus
comprising: a substrate holder configured to hold a substrate; and
a two-fluid nozzle configured to deliver a two-fluid jet onto a
surface of the substrate. The two-fluid nozzle includes a first jet
nozzle configured to emit a first two-fluid jet and a second jet
nozzle configured to emit a second two-fluid jet at a velocity
higher than a velocity of the first two-fluid jet, and the second
jet nozzle surrounds the first jet nozzle.
In an embodiment, the velocity of the second two-fluid jet is not
less than a speed of sound.
In an embodiment, the substrate cleaning apparatus further
comprises a nozzle moving mechanism configured to move the
two-fluid nozzle in a radial direction of the substrate.
In an embodiment, the substrate cleaning apparatus further
comprises a distance adjuster configured to change a distance
between the two-fluid nozzle and the surface of the substrate.
In an embodiment, the substrate cleaning apparatus further
comprises a third jet nozzle disposed inside the first jet nozzle
and configured to emit a third two-fluid jet at a velocity higher
than the velocity of the first two-fluid jet.
In an embodiment, the velocity of the third two-fluid jet is not
less than a speed of sound.
In an embodiment, there is provided a substrate cleaning apparatus
comprising: a substrate holder configured to hold a substrate; and
a two-fluid nozzle configured to deliver a two-fluid jet onto a
surface of the substrate. The two-fluid nozzle includes a first jet
nozzle configured to emit a first fluid jet and a second jet nozzle
configured to emit a second fluid jet at a velocity is higher than
a velocity of the first fluid jet, the second jet nozzle surrounds
the first jet nozzle, and one of the first fluid jet and the second
fluid jet is a two-fluid jet, and other is a gas jet.
In an embodiment, there is provided a substrate processing
apparatus comprising: a polishing unit configured to polish a
substrate; and the above-described substrate cleaning apparatus
configured to clean the substrate polished by the polishing
unit.
According to the above-described embodiment, the second two-fluid
jet having a higher velocity travels toward the surface of the
substrate while surrounding the first two-fluid jet. Since there is
a difference in velocity between the first two-fluid jet and the
second two-fluid jet, the second two-fluid jet converges due to a
contact with the first two-fluid jet. In this manner, since the
second two-fluid jet converges, an incident angle of a shock wave
with respect to the surface of the substrate becomes greater (i.e.,
approaches 90 degrees). As a result, the shock wave impinges on
particles existing in minute recesses formed on the substrate
surface, thereby removing these particles.
In an embodiment, there is provided a substrate cleaning apparatus
comprising: a substrate holder configured to hold a substrate; a
two-fluid nozzle configured to deliver a two-fluid jet onto a
surface of the substrate; a gas supply line configured to supply a
gas into a gas pocket formed in the two-fluid nozzle; a gas supply
valve configured to open and close a gas passage of the gas supply
line; a liquid supply line configured to supply a liquid into a
mixing chamber formed in the two-fluid nozzle; a gas suction line
configured to suck the gas that exists in the gas pocket; a gas
suction valve configured to open and close a gas passage of the gas
suction line; and a valve controller configured to cause the gas
supply valve and the gas suction valve to repeat opening and
closing operations with a same period, the valve controller being
configured to control the operations of the gas supply valve and
the gas suction valve such that the gas suction valve is in an open
state when the gas supply valve is in a closed state.
In an embodiment, the valve controller is configured to cause the
gas suction valve to open while causing the gas supply valve to
close simultaneously.
In an embodiment, the valve controller is configured to cause the
gas suction valve to open before causing the gas supply valve to
close.
In an embodiment, the gas suction line is coupled to the two-fluid
nozzle through a gas discharge port that is located above the
mixing chamber.
In an embodiment, the period is in a range of 0.1 to 1.0
second.
In an embodiment, there is provided a substrate processing
apparatus comprising: a polishing unit configured to polish a
substrate; and the above-described substrate cleaning apparatus
configured to clean the substrate polished by the polishing
unit.
According to the above-described embodiment, the supply of the gas
into the gas pocket of the two-fluid nozzle and the suction of the
gas are alternately repeated. Specifically, the gas is supplied
into the gas pocket when a residual pressure in the gas pocket has
been removed. Therefore, a flow rate of the two-fluid mixture can
largely fluctuate, and as a result, the substrate can be cleaned
efficiently.
In an embodiment, there is provided a substrate cleaning apparatus
comprising: a substrate holder configured to hold a substrate; a
two-fluid nozzle configured to deliver a two-fluid jet onto a
surface of the substrate; a gas supply line configured to supply a
gas into a mixing chamber formed in the two-fluid nozzle; a liquid
supply line configured to supply a liquid into the two-fluid
nozzle; and a droplet-forming device configured to form droplets
from the liquid that has been supplied into the two fluid nozzle
and to supply the droplets into the mixing chamber.
In an embodiment, the droplet-forming device includes a liquid
delivery pipe coupled to the liquid supply line and being in
communication with the mixing chamber, a liquid supply valve
configured to open and close a liquid passage of the liquid supply
line, a liquid suction line configured to suck the liquid flowing
in the liquid delivery pipe, a liquid suction valve configured to
open and close a liquid passage of the liquid suction line, and a
valve controller configured to alternately cause the liquid supply
valve and the liquid suction valve to open and close.
In an embodiment, the droplet-forming device includes a liquid
chamber that is in communication with the liquid supply line, and a
piezoelectric element configured to push the liquid out of the
liquid chamber to form the droplets.
In an embodiment, the two-fluid nozzle has a gas pocket that
deliver the gas from the gas supply line into the mixing chamber,
and the droplet-forming device has a droplet outlet surrounded by
the gas pocket.
In an embodiment, the droplet-forming device has a flange that
protrudes outwardly from the droplet outlet.
In an embodiment, the substrate cleaning apparatus further
comprises an ultrasonic transducer configured to vibrate the
liquid.
In an embodiment, there is provided a substrate processing
apparatus comprising: a polishing unit configured to polish a
substrate; and the above-described substrate cleaning apparatus
configured to clean the substrate polished by the polishing
unit.
According to the above-described embodiment, the droplets are
broken up in the mixing chamber by a gas flow, thereby forming fine
droplets. These fine droplets can easily enter recesses formed on
the surface of the substrate, thereby removing particles existing
in the recesses. Therefore, a cleaning effect of the substrate can
be improved.
In an embodiment, there is provided a substrate cleaning apparatus
comprising: a substrate holder configured to hold and rotate a
substrate; a two-fluid nozzle configured to deliver a two-fluid jet
onto a surface of the substrate; and at least one oscillator that
is to come in contact with the substrate to vibrate the
substrate.
In an embodiment, the oscillator is configured to rotate together
with the substrate while vibrating the substrate.
In an embodiment, the oscillator includes a piezoelectric element,
and a contact member that is mounted to the piezoelectric element
and is to come in contact with the substrate.
In an embodiment, the oscillator is configured to vibrate the
substrate in a direction perpendicular to the surface of the
substrate.
In an embodiment, the oscillator is configured to vibrate the
substrate in a direction parallel to the surface of the
substrate.
In an embodiment, the at least one oscillator comprises at least
one first oscillator configured to vibrate the substrate in a
direction perpendicular to the surface of the substrate and at
least one second oscillator configured to vibrate the substrate in
a direction parallel to the surface of the substrate.
In an embodiment, the at least one oscillator comprises a plurality
of oscillators, and at least two of the plurality of oscillators
are configured to vibrate the substrate at different frequencies
and/or different amplitudes.
In an embodiment, the substrate cleaning apparatus further
comprises: a cleaning-liquid nozzle configured to supply a cleaning
liquid onto a lower surface of the substrate; and an ultrasonic
transducer configured to vibrate the cleaning liquid.
In an embodiment, there is provided a substrate processing
apparatus comprising: a polishing unit configured to polish a
substrate; and the above-described substrate cleaning apparatus
configured to clean the substrate polished by the polishing
unit.
According to the above-described embodiment, the vibration that is
applied to the substrate can make it easier to separate the
particles from the substrate. In this state, the two-fluid jet is
supplied onto the substrate to remove the particles from the
substrate. In this manner, a cleaning efficiency of the substrate
can be enhanced by a combination of the vibration of the substrate
and an impact of the two-fluid jet.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view showing a whole structure of a substrate
processing apparatus incorporating a substrate cleaning apparatus
according to an embodiment;
FIG. 2 is a perspective view showing the substrate cleaning
apparatus, according to the embodiment, used as a second cleaning
unit;
FIG. 3 is a vertical cross-sectional view showing an example of a
two-fluid nozzle;
FIG. 4 is a cross-sectional view taken along line A-A of FIG.
3;
FIG. 5 is a schematic view showing a first two-fluid jet and a
second two-fluid jet ejected from a first jet nozzle and a second
jet nozzle, respectively;
FIG. 6 is a schematic view showing shock waves when the second
two-fluid jet collides with a surface of a wafer;
FIG. 7 is a schematic view showing another embodiment of the
two-fluid nozzle;
FIG. 8 is a schematic view showing the first jet nozzle, the second
jet nozzle, and a third jet nozzle as viewed from an axial
direction thereof;
FIG. 9 is a perspective view showing still another embodiment of
the substrate cleaning apparatus used as the second cleaning
unit;
FIG. 10 is a schematic view showing a structure of the substrate
cleaning apparatus;
FIG. 11 is a graph showing open and closed states of a gas supply
valve and a gas suction valve;
FIG. 12 is a graph showing a flow rate of a two-fluid mixture when
the gas supply valve and the gas suction valve are periodically
opened and closed according to timings shown in FIG. 11;
FIG. 13 is a graph showing open and closed states of the gas supply
valve and the gas suction valve according to another
embodiment;
FIG. 14 is a perspective view showing still another embodiment of
the substrate cleaning apparatus used as the second cleaning
unit;
FIG. 15 is a schematic view showing an embodiment of a structure of
the substrate cleaning apparatus;
FIG. 16 is a graph showing open and closed states of a liquid
supply valve and a liquid suction valve;
FIG. 17 is a graph showing a flow rate of a liquid when the liquid
supply valve and the liquid suction valve are periodically opened
and closed according to timings shown in FIG. 16;
FIG. 18 is a graph showing a flow rate of the liquid when the
liquid supply valve is periodically opened and closed while the
liquid suction valve is closed;
FIG. 19 is a schematic view showing the two-fluid jet when
colliding with the surface of the wafer;
FIG. 20 is a schematic view showing another embodiment of a
structure of the substrate cleaning apparatus;
FIG. 21 is a vertical cross-sectional view of a piezoelectric
injector;
FIG. 22 is a bottom view of the piezoelectric injector;
FIG. 23 is an enlarged view showing a liquid chamber and a
piezoelectric element shown in FIG. 21;
FIG. 24 is a view showing a state in which a voltage is applied to
the piezoelectric element shown in FIG. 23;
FIG. 25 is a view showing a flange formed on a lower end of a
liquid delivery pipe;
FIG. 26 is a view showing a flange formed on a lower end of the
piezoelectric injector;
FIG. 27 is a view showing an ultrasonic transducer provided on the
liquid delivery pipe;
FIG. 28 is a view showing an ultrasonic transducer provided on a
distribution passage in the piezoelectric injector;
FIG. 29 is a perspective view showing still another embodiment of
the substrate cleaning apparatus used as the second cleaning
unit;
FIG. 30 is a cross-sectional view showing a chuck of the substrate
cleaning apparatus;
FIG. 31 is an enlarged view of an oscillator;
FIG. 32 is a plan view of a substrate holder;
FIG. 33 is a schematic view showing a state in which the oscillator
is vibrating the wafer;
FIG. 34 is a schematic view showing a state in which the two-fluid
jet is delivered onto the surface of the wafer while the oscillator
is vibrating the wafer;
FIG. 35 is a view showing still another embodiment;
FIG. 36 is a view showing still another embodiment;
FIG. 37 is a view showing still another embodiment;
FIG. 38 is a plan view of a cleaning-liquid nozzle;
FIG. 39 is a perspective view of the cleaning-liquid nozzle;
FIG. 40 is an enlarged cross-sectional view of the cleaning-liquid
nozzle;
FIG. 41 is a plan view of the cleaning-liquid nozzle according to
another example;
FIG. 42 is a schematic view showing a conventional two-fluid
cleaning apparatus;
FIG. 43 is a schematic view showing a two-fluid jet ejected from a
conventional jet nozzle;
FIG. 44 is a schematic view showing shock waves when the two-fluid
jet collides with a surface of a substrate;
FIG. 45 is a schematic view showing a structure of the two-fluid
cleaning apparatus shown in FIG. 42;
FIG. 46 is a graph a showing open and closed states of a gas supply
valve;
FIG. 47 is a graph showing a flow rate of a two-fluid mixture when
the gas supply valve is periodically opened and closed according to
timings shown in FIG. 46;
FIG. 48 is a schematic view showing a droplet of the two-fluid
mixture; and
FIG. 49 is a schematic view showing the droplet when colliding with
the surface of the substrate.
DESCRIPTION OF EMBODIMENTS
Embodiments will be described with reference to the drawings. FIG.
1 is a plan view showing a whole structure of a substrate
processing apparatus incorporating a substrate cleaning apparatus
according to an embodiment. As shown in FIG. 1, the substrate
processing apparatus includes an approximately-rectangular housing
10, and a loading port 12 on which a substrate cassette is placed.
The substrate cassette houses therein a large number of substrates,
such as wafers. The loading port 12 is disposed adjacent to the
housing 10. The loading port 12 can be mounted with an open
cassette, a SMIF (Standard Manufacturing Interface) pod, or a FOUP
(Front Opening Unified Pod). Each of the SMIF and the FOUP is an
airtight container which houses a substrate cassette therein and
which, by covering it with a partition wall, can keep its internal
environment isolated from an external environment.
In the housing 10, there are disposed a plurality of (e.g., four in
this embodiment) polishing units 14a to 14d, a first cleaning unit
16 and a second cleaning unit 18 each for cleaning a polished
substrate, and a drying unit 20 for drying a cleaned substrate. The
polishing units 14a to 14d are arranged along a longitudinal
direction of the substrate processing apparatus, and the cleaning
units 16, 18 and the drying unit 20 are also arranged along the
longitudinal direction of the substrate processing apparatus.
A first substrate transfer robot 22 is disposed in an area
surrounded by the loading port 12, the polishing unit 14a, and the
drying unit 20. Further, a substrate transport unit 24 is disposed
parallel to the polishing units 14a to 14d. The first substrate
transfer robot 22 receives a substrate, to be polished, from the
loading port 12 and transfers the substrate to the substrate
transport unit 24, and further receives a dried substrate from the
drying unit 20 and returns the dried substrate to the loading port
12. The substrate transport unit 24 transports a substrate received
from the first substrate transfer robot 22, and transfers the
substrate between the polishing units 14a to 14d. Each of the
polishing units is configured to polish a surface of a substrate,
such as a wafer, by bringing the substrate into sliding contact
with a polishing surface while supplying a polishing liquid
(slurry) onto the polishing surface.
A second substrate transfer robot 26 for transporting a substrate
between the cleaning units 16, 18 and the substrate transport unit
24 is provided between the first cleaning unit 16 and the second
cleaning unit 18. A third substrate transfer robot 28 for
transporting a substrate between the second cleaning unit 18 and
the drying unit 20 is provided between these units 18, 20. Further,
an operation controller 30 for controlling operations of each of
the units of the substrate processing apparatus is provided in the
housing 10.
The first cleaning unit 16 is a substrate cleaning apparatus
configured to clean a substrate by scrubbing both a front surface
and a rear surface of the substrate with roll sponges in the
presence of a chemical liquid. The second cleaning unit 18 is a
substrate cleaning apparatus of two-fluid type according to an
embodiment. The drying unit 20 is a spin drying apparatus
configured to hold a substrate, eject IPA vapor from a moving
nozzle to dry the substrate, and rotate the substrate at a high
speed to further dry the substrate.
The substrate is polished by at least one of the polishing units
14a to 14d. The polished substrate is cleaned by the first cleaning
unit 16 and the second cleaning unit 18, and the cleaned substrate
is then dried by the drying unit 20.
FIG. 2 is a perspective view showing the substrate cleaning
apparatus, according to an embodiment, used as the second cleaning
unit 18. As shown in FIG. 2, this substrate cleaning apparatus
includes a substrate holder 41 configured to horizontally hold and
rotate a wafer W, which is an example of a substrate, a two-fluid
nozzle 42 configured to deliver a two-fluid jet to an upper surface
of the wafer W, and a nozzle arm 44 that holds this two-fluid
nozzle 42. A first gas supply source 55, a second gas supply source
56, and a liquid supply source 57 are coupled to the two-fluid
nozzle 42.
The substrate holder 41 includes a plurality of (e.g., four in FIG.
2) chucks 45 for holding a periphery of the wafer W, and a motor 48
coupled to the chucks 45. The chucks 45 hold the wafer W
horizontally, and in this state, the wafer W is rotated about its
central axis by the motor 48.
The two-fluid nozzle 42 is disposed above the wafer W. The
two-fluid nozzle 42 is mounted to one end of the nozzle arm 44, and
a pivot shaft 50 is coupled to other end of the nozzle arm 44. The
two-fluid nozzle 42 is coupled to a nozzle moving mechanism 51
through the nozzle arm 44 and the pivot shaft 50. More
specifically, the pivot shaft 50 is coupled to the nozzle moving
mechanism 51 that is configured to cause the nozzle arm 44 to
pivot. This nozzle moving mechanism 51 is configured to rotate the
pivot shaft 50 through a predetermined angle to thereby cause the
nozzle arm 44 to pivot in a plane parallel to the wafer W. As the
nozzle arm 44 pivots, the two-fluid nozzle 42, which is supported
by the nozzle arm 44, moves in a radial direction of the wafer
W.
The nozzle moving mechanism 51 is coupled to a nozzle elevating
mechanism 52 for elevating and lowering the pivot shaft 50, so that
the two-fluid nozzle 42 can vertically move relative to the wafer
W. This nozzle elevating mechanism 52 serves as a distance adjuster
configured to change a distance between the two-fluid nozzle 42 and
the surface of the wafer W.
The wafer W is cleaned as follows. First, the wafer W is rotated
about its central axis by the substrate holder 41. In this state,
the two-fluid nozzle 42 supplies the two-fluid jet onto the upper
surface of the wafer W, and further moves in the radial direction
of the wafer W. The upper surface of the wafer W is cleaned with
the two-fluid jet.
FIG. 3 is a vertical cross-sectional view showing an example of the
two-fluid nozzle 42, and FIG. 4 is a cross-sectional view taken
along line A-A of FIG. 3. As shown in FIG. 3, the two-fluid nozzle
42 includes a first jet nozzle 61, a second jet nozzle 62 that
surrounds the first jet nozzle 61, and a liquid container 65 in
which a liquid chamber 66 is formed. The liquid chamber 66 is in
communication with the first jet nozzle 61 and the second jet
nozzle 62. The liquid container 65 is coupled to an upper end of
the second jet nozzle 62, and a lower end of the first jet nozzle
61 is located at the same height as a lower end of the second jet
nozzle 62. As shown in FIG. 4, the first jet nozzle 61 and the
second jet nozzle 62 are coaxially arranged.
As shown in FIG. 3, the liquid container 65 has a liquid
introduction port 74 that is in communication with the liquid
chamber 66. The liquid introduction port 74 is coupled to the
liquid supply source 57. A liquid (e.g., pure water) is supplied
through the liquid introduction port 74 into the liquid chamber 66.
The first jet nozzle 61 extends through the liquid container 65. A
plurality of first connection passages 71, which are in
communication with the liquid chamber 66, are formed in the first
jet nozzle 61. A second connection passage 72, which provides a
fluid communication between the second jet nozzle 62 and the liquid
chamber 66, is formed in a lower end of the liquid container 65.
This second connection passage 72 surrounds the first jet nozzle
61.
A first gas introduction port 75, which is coupled to the first gas
supply source 55, is formed on an upper end of the first jet nozzle
61. A second gas introduction port 76, which is coupled to the
second gas supply source 56, is formed on an upper end of the
second jet nozzle 62. The first gas supply source 55 supplies a
first gas through the first gas introduction port 75 into the first
jet nozzle 61, while the second gas supply source 56 supplies a
second gas, whose pressure is higher than that of the first gas,
through the second gas introduction port 76 into the second jet
nozzle 62.
The liquid, the first gas, and the second gas are simultaneously
supplied into the two-fluid nozzle 42. The liquid fills the liquid
chamber 66, and then flows through the first connection passages 71
into the first jet nozzle 61, while the liquid passes through the
second connection passage 72 into the second jet nozzle 62. In the
first jet nozzle 61, the first gas and the liquid are mixed to form
a first two-fluid jet. In the second jet nozzle 62, the second gas
and the liquid are mixed to form a second two-fluid jet. The first
gas and the second gas may be of the same type or may be of
different types.
The second gas introduced into the second jet nozzle 62 has a
higher pressure than a pressure of the first gas introduced into
the first jet nozzle 61. Therefore, the second two-fluid jet
travels at a higher velocity than a velocity of the first two-fluid
jet. Specifically, the velocity of the second two-fluid jet is
preferably equal to or more than a speed of sound. The reason for
this is that strong shock waves are generated when the second
two-fluid jet collides with the surface of the wafer W. The speed
of sound is 331.45 m/s under conditions of a temperature of
0.degree. C. and an atmospheric pressure of 1 atm.
FIG. 5 is a schematic view showing the first two-fluid jet and the
second two-fluid jet ejected from the first jet nozzle 61 and the
second jet nozzle 62, respectively. There is a difference in
velocity between the first two-fluid jet and the second two-fluid
jet. Therefore, as shown in FIG. 5, the second two-fluid jet
converges due to contact with the first two-fluid jet. In this
manner, since the second two-fluid jet converges, an incident angle
of the shock wave with respect to the surface of the wafer W
becomes larger (i.e., approaches 90 degrees), as shown in FIG. 6.
As a result, the shock waves impinge on particles existing in
minute recesses formed on the surface of the substrate, thus
removing these particles. In particular, fine particles, having a
size of at most 100 nm and existing in the recesses (e.g., stepped
portions of patterns and scratches), can be removed.
The above-discussed structure of the two-fluid nozzle shown in FIG.
3 is given by way of an example, and other structure may be
employed. For example, a first gas and a first liquid may be
supplied respectively from a first gas supply source and a first
liquid supply source into the first jet nozzle 61, while a second
gas and a second liquid may be supplied respectively from a second
gas supply source and a second liquid supply source into the second
jet nozzle 62. In this case, types of the first gas and the first
liquid may be different from types of the second gas and the second
liquid. For example, functional water (e.g., hydrogen water,
ammonia water, or liquid containing isopropyl alcohol) may be used
for one of the first liquid and the second liquid, while pure water
may be used for the other.
One of the first fluid jet ejected from the first jet nozzle 61 and
the second fluid jet ejected from the second jet nozzle 62 may be a
two-fluid jet, while the other may be a gas jet. For example, the
first jet nozzle 61 may be constructed to emit a low-speed gas jet,
while the second jet nozzle 62 may be constructed to emit a
high-speed two-fluid jet. In another example, the second jet nozzle
62 may be constructed to emit a high-speed gas jet, while the first
jet nozzle 61 may be constructed to emit a low-speed two-fluid
jet.
FIG. 7 is a schematic view showing another embodiment of the
two-fluid nozzle. Structures that are not described particularly in
this embodiment are identical to those of the embodiment shown in
FIG. 3. In this embodiment, a third jet nozzle 79 is disposed
inside the first jet nozzle 61. The first jet nozzle 61, the second
jet nozzle 62, and the third jet nozzle 79 are arranged coaxially
as shown in FIG. 8. The third jet nozzle 79 emits a third two-fluid
jet at a velocity higher than the velocity of the first two-fluid
jet. More specifically, the velocities of the second two-fluid jet
and the third two-fluid jet are higher than the velocity of the
first two-fluid jet. The velocities of the second two-fluid jet and
the third two-fluid jet are preferably not less than the speed of
sound. The second two-fluid jet having the higher velocity
converges due to a contact with the first two-fluid jet having the
lower velocity, and the third two-fluid jet having the higher
velocity spreads due to a contact with the first two-fluid jet
having the lower velocity.
Either the first fluid jet ejected from the first jet nozzle 61 or
the second and third fluid jets ejected from the second and third
jet nozzles 62, 79 may be a two-fluid jet, while the other may be a
gas jet. For example, the first jet nozzle 61 may be constructed to
emit a gas jet having a low velocity, while the second and third
jet nozzles 62, 79 may be each constructed to emit a two-fluid jet
having a high velocity. In another example, the second and third
jet nozzles 62, 79 may be each constructed to emit a gas jet having
a high velocity, while the first jet nozzle 61 may be constructed
to emit a two-fluid jet having a low velocity.
FIG. 9 is a perspective view showing still another embodiment of
the substrate cleaning apparatus used as the second cleaning unit
18. Structures and operations of the substrate cleaning apparatus
that are not described particularly in this embodiment are
identical to those of the embodiment shown in FIG. 2, and
repetitive descriptions thereof are omitted. As shown in FIG. 9,
this substrate cleaning apparatus includes substrate holder 41
configured to horizontally hold and rotate a wafer W, which is an
example of a substrate, two-fluid nozzle 42 configured to deliver a
two-fluid jet onto an upper surface of the wafer W, and nozzle arm
44 that holds this two-fluid nozzle 42. A gas supply line 80, a gas
suction line 81, and a liquid supply line 82 are coupled to the
two-fluid nozzle 42.
FIG. 10 is a schematic view showing a structure of the substrate
cleaning apparatus. As shown in FIG. 10, the gas supply line 80
that supplies a gas into a gas pocket 90 formed in the two-fluid
nozzle 42, the liquid supply line 82 that supplies a liquid into a
mixing chamber 91 formed in the two-fluid nozzle 42, and the gas
suction line 81 that sucks a gas existing in the gas pocket 90 are
coupled to the two-fluid nozzle 42.
The two-fluid nozzle 42 has a gas introduction port 94 provided on
an upper portion of the two-fluid nozzle 42, and the gas supply
line 80 is coupled to the two-fluid nozzle 42 through the gas
introduction port 94. The two-fluid nozzle 42 further has a gas
discharge port 95 provided on the upper portion of the two-fluid
nozzle 42, and the gas suction line 81 is coupled to the two-fluid
nozzle 42 through the gas discharge port 95. The gas introduction
port 94 is located at a position higher than the gas discharge port
95.
The liquid supply line 82 extends downwardly through the gas pocket
90 of the two-fluid nozzle 42. The liquid supply line 82 has a
liquid outlet 82a located in the two-fluid nozzle 42. The gas
pocket 90 is located above the liquid outlet 82a of the liquid
supply line 82, and the mixing chamber 91 is located below the
liquid outlet 82a of the liquid supply line 82. The gas pocket 90
and the mixing chamber 91 are in communication with each other.
The liquid, such as pure water, is supplied through the liquid
supply line 82 into the mixing chamber 91 formed in the two-fluid
nozzle 42. The liquid may be delivered in the liquid supply line 82
by a pump that pressurizes the liquid, or may be delivered in the
liquid supply line 82 by an attraction of a negative pressure
produced in the two-fluid nozzle 42 by the gas suction line 81.
In order to prevent the gas suction line 81 from sucking the liquid
in the two-fluid nozzle 42, the gas discharge port 95 is located
above the mixing chamber 91 of the two-fluid nozzle 42 (i.e., at a
position higher than the liquid outlet 82a of the liquid supply
line 82).
The gas supply line 80 is provided with a gas supply valve 101 and
a filter 102. The gas (e.g., inert gas, such as nitrogen gas)
flowing in the gas supply line 80 passes through the gas supply
valve 101 and the filter 102 in this order, and then flows through
the gas introduction port 94 into the gas pocket 90 of the
two-fluid nozzle 42. The liquid from the liquid supply line 82 and
the gas from the gas supply line 80 are mixed in the mixing chamber
91 to form a high-pressure two-fluid jet.
The gas supply valve 101 operates so as to repeatedly open and
close a gas passage of the gas supply line 80 with a predetermined
period. Therefore, the gas is intermittently supplied into the gas
pocket 90. As a result, a flow rate of the two-fluid jet
periodically varies. The two-fluid jet that is pulsating in this
manner is supplied onto the surface of the substrate to thereby
remove abrasive grains and polishing debris from the surface of the
substrate.
A vacuum source 97, such as a vacuum pump, is coupled to the gas
suction line 81. This gas suction line 81 is provided with a gas
suction valve 103. The gas suction valve 103 operates so as to
repeatedly open and close a gas passage of the gas suction line 81
with the same period as that of the gas supply valve 101.
Therefore, the gas suction line 81 intermittently sucks the gas
existing in the gas pocket 90. A flow control valve (e.g., mass
flow controller), an air operated valve, an on-off valve, or the
like may be used for the gas supply valve 101 and the gas suction
valve 103.
During the supply of the liquid into the mixing chamber 91, opening
and closing operations of the gas supply valve 101 and the gas
suction valve 103 are repeated with a predetermined period (e.g.,
0.1 to 1.0 second) so as to repeat the supply of the gas into the
gas pocket 90 and the suction of the gas from the gas pocket 90
alternately. The gas supply valve 101 and the gas suction valve 103
are coupled to a valve controller 105, so that the opening and
closing operations of the gas supply valve 101 and the gas suction
valve 103 are controlled by the valve controller 105.
FIG. 11 is a graph showing open and closed states of the gas supply
valve 101 and the gas suction valve 103. In FIG. 11, vertical axis
represents whether the gas supply valve 101 and the gas suction
valve 103 are in the open state or the closed state, and horizontal
axis represents time. As can be seen from FIG. 11, the gas supply
valve 101 and the gas suction valve 103 repeat their opening and
closing operations with the same period, while the open and closed
states of the gas suction valve 103 are opposite to the open and
closed states of the gas supply valve 101. More specifically, the
gas suction valve 103 is closed at the same time as the gas supply
valve 101 is opened, and the gas suction valve 103 is opened at the
same time as the gas supply valve 101 is closed.
In this manner, as the gas supply valve 101 and the gas suction
valve 103 are alternately opened and closed with the same period,
the supply of the gas into the gas pocket 90 and the suction of the
gas from the gas pocket 90 are alternately performed. The opening
and closing operations of the gas supply valve 101 and the gas
suction valve 103 are controlled by the valve controller 105. As
shown in FIG. 11, the valve controller 105 is configured to cause
the gas supply valve 101 and the gas suction valve 103 to repeat
the opening and closing operations with the same period.
When the gas supply valve 101 is in a closed state, the gas suction
valve 103 is in an open state. The gas in the gas pocket 90 is
sucked through the gas suction line 81, and as a result, a residual
pressure in the gas pocket 90 is removed. FIG. 12 is a graph
showing a flow rate of the two-fluid jet when the gas supply valve
101 and the gas suction valve 103 are periodically opened and
closed according to timings shown in FIG. 11. Since the residual
pressure in the gas pocket 90 is removed before the gas is supplied
into the gas pocket 90, the two-fluid jet pulsates greatly as shown
in FIG. 12. As a result, the two-fluid jet can clean the surface of
the substrate highly efficiently.
FIG. 13 is a graph showing the open and closed states of the gas
supply valve 101 and the gas suction valve 103 according to another
embodiment. Structures and operations that are not described
particularly in this embodiment are identical to those of the
above-described embodiment, and repetitive descriptions thereof are
omitted. This embodiment is the same as the above-described
embodiment in that the gas suction valve 103 is closed at the same
time as the gas supply valve 101 is opened, but is different in
that the gas suction valve 103 is opened before the gas supply
valve 101 is closed. An opening and closing period of the gas
suction valve 103 is the same as an opening and closing period of
the gas supply valve 101.
According to the embodiment shown in FIG. 13, when the gas supply
valve 101 is closed, the residual pressure is removed without
delay. In this case also, the gas suction valve 103 is in the open
state when the gas supply valve 101 is in the closed state. The
supply of the gas into the gas pocket 90 and the suction of the gas
from the gas pocket 90 are alternately repeated. As a result, the
flow rate of the two-fluid jet pulsates largely in almost the same
manner as in the graph shown in FIG. 12. Therefore, the two-fluid
jet can clean the surface of the substrate highly efficiently.
When the gas supply valve 101 is in the closed state, the gas
suction valve 103 may not be in the open state at all times. For
example, the gas suction valve 103 may be closed immediately before
the gas supply valve 101 is opened (i.e., when the gas supply valve
101 is in the closed state).
FIG. 14 is a perspective view showing still another embodiment of
the substrate cleaning apparatus used as the second cleaning unit
18. Structures and operations of the substrate cleaning apparatus
that are not described particularly in this embodiment are
identical to those of the embodiment shown in FIG. 2, and
repetitive descriptions thereof are omitted. As shown in FIG. 14,
this substrate cleaning apparatus includes substrate holder 41
configured to horizontally hold and rotate a wafer W, which is an
example of a substrate, two-fluid nozzle 42 configured to deliver a
two-fluid jet onto an upper surface of the wafer W, and nozzle arm
44 that holds this two-fluid nozzle 42. A gas supply line 111, a
liquid supply line 112, and a liquid suction line 113 are coupled
to the two-fluid nozzle 42.
FIG. 15 is a schematic view showing an embodiment of a structure of
the substrate cleaning apparatus. As shown in FIG. 15, the gas
supply line 111 that supplies a gas through a gas pocket 120, which
is formed in the two-fluid nozzle 42, into a mixing chamber 121,
the liquid supply line 112 that supplies a liquid (e.g., pure
water) into a liquid delivery pipe 137 communicating with the
mixing chamber 121, and the liquid suction line 113 that sucks the
liquid flowing in the liquid delivery pipe 137 are coupled to the
two-fluid nozzle 42.
The gas pocket 120, the mixing chamber 121, and the liquid delivery
pipe 137 are located in the two-fluid nozzle 42. The liquid
delivery pipe 137 is surrounded by an outer cylinder 138, and the
gas pocket 120 is formed between the liquid delivery pipe 137 and
the outer cylinder 138. The mixing chamber 121 is formed in the
outer cylinder 138, and is located below the liquid delivery pipe
137 and the gas pocket 120. The gas pocket 120 is in communication
with the mixing chamber 121. The gas from the gas supply line 111
is introduced through the gas pocket 120 into the mixing chamber
121.
The gas supply line 111 is provided with a filter 132. The gas
(e.g., inert gas, such as nitrogen gas) flowing in the gas supply
line 111 passes through the filter 132, and then flows into the gas
pocket 120 of the two-fluid nozzle 42.
The liquid supply line 112 is provided with a liquid supply valve
141 for opening and closing a liquid passage of the liquid supply
line 112. The liquid suction line 113 is provided with a liquid
suction valve 142 for opening and closing a liquid passage of the
liquid suction line 113. A flow control valve (e.g., mass flow
controller), an air operated valve, an on-off valve, or the like
may be used for the liquid supply valve 141 and the liquid suction
valve 142.
One end of the liquid suction line 113 is coupled to a side surface
of the liquid delivery pipe 137. More specifically, the liquid
delivery pipe 137 has a liquid suction port 139 at the side surface
thereof, and the liquid suction line 113 is coupled to this liquid
suction port 139. The other end of the liquid suction line 113 is
coupled to a liquid suction pump 148. The liquid supply line 112 is
coupled to an upper open end of the liquid delivery pipe 137. The
liquid supply valve 141 and the liquid suction valve 142 are
coupled to valve controller 135, so that opening and closing
operations of the liquid supply valve 141 and the liquid suction
valve 142 are controlled by the valve controller 135. More
specifically, the opening and closing operations of the liquid
supply valve 141 and the liquid suction valve 142 are repeated with
a predetermined period so as to alternately repeat the supply of
the liquid into the liquid delivery pipe 137 and the suction of the
liquid from the liquid delivery pipe 137.
FIG. 16 is a graph showing open and closed states of the liquid
supply valve 141 and the liquid suction valve 142. In FIG. 16,
vertical axis represents whether the liquid supply valve 141 and
the liquid suction valve 142 are in the open state or the closed
state, and horizontal axis represents time. As can be seen from
FIG. 16, the liquid supply valve 141 and the liquid suction valve
142 repeat their opening and closing operations with the same
period, while the open and closed states of the liquid suction
valve 142 are opposite to the open and closed states of the liquid
supply valve 141. More specifically, the liquid suction valve 142
is closed at the same time as the liquid supply valve 141 is
opened, and the liquid suction valve 142 is opened at the same time
as the liquid supply valve 141 is closed.
In this manner, as the liquid supply valve 141 and the liquid
suction valve 142 are alternately opened and closed with the same
period, the supply of the liquid into the liquid delivery pipe 137
and the suction of the liquid from the liquid delivery pipe 137 are
alternately performed. The opening and closing operations of the
liquid supply valve 141 and the liquid suction valve 142 are
controlled by the valve controller 135. As shown in FIG. 16, the
valve controller 135 causes the liquid supply valve 141 and the
liquid suction valve 142 to alternately open and close with the
same period.
FIG. 17 is a graph showing a flow rate of the liquid when the
liquid supply valve 141 and the liquid suction valve 142 are
periodically opened and closed according to timings shown in FIG.
16. Since the supply and the suction of the liquid are alternately
performed, the flow rate of the liquid flowing in the liquid
delivery pipe 137 greatly fluctuates, as shown in FIG. 17. As a
result, the liquid is converted into droplets, which are discharged
through a droplet outlet 140 that is provided at a lower end of the
liquid delivery pipe 137. The droplets are supplied into the mixing
chamber 121 located below the liquid delivery pipe 137.
FIG. 18 is a graph showing the flow rate of the liquid when the
liquid supply valve 141 is periodically opened and closed while the
liquid suction valve 142 is closed. As shown in FIG. 18, when only
the liquid supply valve 141 is opened and closed, the flow rate of
the liquid flowing in the liquid delivery pipe 137 does not
fluctuate largely. As can be seen from a comparison of the graph
shown in FIG. 17 and the graph shown in FIG. 18, the liquid flowing
in the liquid delivery pipe 137 can be converted into the droplets
by repeating the supply and the suction of the liquid
alternately.
The gas pocket 120 is formed so as to surround the liquid delivery
pipe 137, and the droplet outlet 140 of the liquid delivery pipe
137 is surrounded by the gas pocket 120. A gas flow travelling
toward the mixing chamber 121 is formed in this gas pocket 120. The
droplets discharged from the liquid outlet 140 are broken up in the
mixing chamber 121 by the gas flow, thereby forming finer droplets.
Such fine droplets and the gas are mixed in the mixing chamber 121
to form the two-fluid jet.
FIG. 19 is a schematic view showing the two-fluid jet when
colliding with the surface of the wafer W. As shown in FIG. 19, the
fine droplets, which constitute the two-fluid jet, enter minute
recesses (e.g., stepped portions of patterns and scratches) formed
on the surface of the wafer W, thus removing fine particles of at
most 100 nm that exist in these recesses.
In this embodiment, a droplet-forming device 150 is constituted by
the liquid delivery pipe 137 that is coupled to the liquid supply
line 112 and is in communication with the mixing chamber 121, the
liquid supply valve 141 configured to open and close the liquid
passage of the liquid supply line 112, the liquid suction line 113
configured to suck the liquid flowing in the liquid delivery pipe
137, the liquid suction valve 142 configured to open and close the
liquid passage of the liquid suction line 113, and the valve
controller 135 configured to cause the liquid supply valve 141 and
the liquid suction valve 142 to alternately open and close.
FIG. 20 is a schematic view showing another embodiment of a
structure of the substrate cleaning apparatus. Structures that are
not described particularly in this embodiment are identical to
those of the embodiment shown in FIG. 15, and repetitive
descriptions thereof are omitted.
As shown in FIG. 20, a droplet-forming device 150 according to this
embodiment includes a piezoelectric injector (or a piezoelectric
injection device) 155. The piezoelectric injector 155 is disposed
in the two-fluid nozzle 42. The gas pocket 120 is formed around the
piezoelectric injector 155, and the mixing chamber 121 is located
below the piezoelectric injector 155. This piezoelectric injector
155 is coupled to the liquid supply line 112, so that the liquid is
supplied through the liquid supply line 112. The liquid is
converted into droplets by the piezoelectric injector 155, and
these droplets are supplied into the mixing chamber 121. In this
embodiment, the liquid suction line 113, the liquid suction valve
142, and the valve controller 135, which are described above, are
not provided. The liquid supply valve 141 may not be provided.
FIG. 21 is a vertical cross-sectional view of the piezoelectric
injector 155, and FIG. 22 is a bottom view of the piezoelectric
injector 155. The piezoelectric injector 155 includes a plurality
of liquid chambers 157, a plurality of piezoelectric elements 158
that adjoin these liquid chambers 157, respectively, and a
distribution passage 159 coupled to the liquid chambers 157. The
multiple liquid chambers 157 are in communication with the liquid
supply line 112 through the distribution passage 159. Further, the
multiple liquid chambers 157 are in communication with a plurality
of droplet outlets 140, respectively. These droplet outlets 140 are
formed in a lower surface of the piezoelectric injector 155. The
droplet outlets 140 are surrounded by the gas pocket 120. An
electric power supply (not shown) is coupled to each piezoelectric
element 158, so that a voltage is periodically applied to each
piezoelectric element 158.
FIG. 23 is an enlarged view showing the liquid chamber 157 and the
piezoelectric element 158 shown in FIG. 21, and FIG. 24 is a view
showing a state in which the voltage is applied to the
piezoelectric element 158 shown in FIG. 23. The piezoelectric
element 158 is in contact with the liquid in the liquid chamber
157. When the voltage is applied to the piezoelectric element 158,
the piezoelectric element 158 becomes deformed as shown in FIG. 24.
As a result, the liquid, filling the liquid chamber 157, is pushed
out by the deformed piezoelectric element 158, and is discharged as
a droplet through the liquid outlet 140.
The voltage is periodically applied to the piezoelectric element
158 to thereby cause the piezoelectric element 158 to continuously
eject droplets into the mixing chamber 121. The droplets are broken
up in the mixing chamber 121 by the gas flow, thereby forming finer
droplets. Such fine droplets and the gas are mixed in the mixing
chamber 121 to form the two-fluid jet. As shown in FIG. 19, the
fine droplets, which constitute the two-fluid jet, enter the minute
recesses (e.g., stepped portions of patterns and scratches) formed
on the surface of the wafer, thus removing fine particles of at
most 100 nm that exist in these recesses.
In the above-described embodiment, the droplets are supplied into
the mixing chamber 121, and are converted into finer droplets by a
collision with the gas flow. In order to accelerate the collision
between the droplets and the gas flow, it is preferable to generate
a turbulent flow of the gas in the mixing chamber 121.
Specifically, as shown in FIG. 25 and FIG. 26, the droplet-forming
device 150 may have a flange 165 that protrudes outwardly from the
droplet outlet 140. In an example shown in FIG. 25, the flange 165
is formed on the lower end of the liquid delivery pipe 137. In an
example shown in FIG. 26, the flange 165 is formed on a lower end
of the piezoelectric injector 155.
The flange 165 is located in the gas pocket 120. When the gas flow
travels over the flange 165, the gas flow is disturbed to form an
inward vortex flow. Such a vortex flow collides with the droplets
discharged from the droplet outlet 140, thereby converting the
droplets into finer droplets. In order to generate a stronger
vortex flow of the gas, the flow velocity of the gas is preferably
not less than the speed of sound.
In order to further enhance the cleaning performance of the
two-fluid jet, an ultrasonic transducer 107 that vibrates the
liquid before forming the droplets may be provided, as shown in
FIG. 27 and FIG. 28. In an example shown in FIG. 27, the ultrasonic
transducer 107 surrounds a part of the liquid delivery pipe 137. In
an example shown in FIG. 28, the ultrasonic transducer 107
surrounds a part of the distribution passage 159 in the
piezoelectric injector 155. The ultrasonic transducer 107 may be
provided on the liquid supply line 112. A frequency of the
vibration generated by the ultrasonic transducer 107 is preferably
in a range of several tens of Hz to several MHz. Furthermore, a
plurality of ultrasonic transducers 107, which can generate
vibrations at different frequencies, may be provided along the
liquid delivery pipe 137 or the distribution passage 159. By
vibrating the liquid at the different frequencies, particles having
different sizes can be removed from the wafer W. The ultrasonic
transducer 107 can vibrate the droplets discharged from the droplet
outlet 140, so that the particles can be removed from the wafer
more effectively.
FIG. 29 is a perspective view showing still another embodiment of
the substrate cleaning apparatus used as the second cleaning unit
18. Structures and operations of the substrate cleaning apparatus
that are not described particularly in this embodiment are
identical to those of the embodiment shown in FIG. 2, and
repetitive descriptions thereof are omitted. As shown in FIG. 29,
this substrate cleaning apparatus includes substrate holder 41
configured to hold and rotate a wafer W, which is an example of a
substrate, two-fluid nozzle 42 configured to deliver a two-fluid
jet onto an upper surface of the wafer W, and nozzle arm 44 that
holds this two-fluid nozzle 42.
A gas supply line 175 and a liquid supply line 177 are coupled to
the two-fluid nozzle 42. A gas and a liquid are supplied through
the gas supply line 175 and the liquid supply line 177 to the
two-fluid nozzle 42, and are mixed in the two-fluid nozzle 42 to
form a two-fluid mixture. This two-fluid mixture is ejected from
the two-fluid nozzle 42 onto the surface of the wafer W.
The substrate holder 41 includes a plurality of (e.g., six in FIG.
29) chucks 45 for holding a periphery of the wafer W, and a motor
48 coupled to the chucks 45. The chucks 45 hold the wafer W, and in
this state, the wafer W is rotated about its central axis by the
motor 48.
FIG. 30 is an enlarged cross-sectional view of the chuck 45. As
shown in FIG. 30, the chuck is provided with an oscillator 181 that
is configured to vibrate the wafer W while being in contact with a
periphery of the wafer W. The oscillator 181 has a contact surface
182 lying parallel to the surface of the wafer W. This contact
surface 182 is to come in contact with a lower surface of the
periphery of the wafer W when the wafer W is supported by the
chucks 45. All chucks 45 are provided with oscillators 181,
respectively, and these oscillators 181 are arranged along the
periphery of the wafer W at equal intervals. When the chucks 45 are
rotated by the motor 48, the oscillators 181 are rotated together
with the chucks 45. Therefore, the oscillators 181 vibrate the
wafer W while being rotated together with the wafer W.
FIG. 31 is an enlarged view of the oscillator 181. As shown in FIG.
31, the oscillator 181 includes a piezoelectric element (or a piezo
element) 186, and a contact member 187 mounted to the piezoelectric
element 186. The oscillator 181 is disposed on the chuck 45 such
that the contact member 187 comes in contact with the lower surface
of the periphery of the wafer W. Therefore, a surface of the
contact member 187 constitutes a contact surface 182 that is to
come in contact with the lower surface of the periphery of the
wafer W.
The contact member 187 serves to protect the piezoelectric element
186 from the liquid supplied to the wafer W and to protect the
wafer W from the piezoelectric element 186. For example, the
contact member 187 is a sheet member made of Teflon (registered
trademark), PEEK (polyether ether ketone) resin, quartz, or the
like. This contact member 187 may be omitted. In this case, the
above-described contact surface 182 of the oscillator 181, which is
to come in contact with the lower surface of the wafer W, is
constituted by a surface of the piezoelectric element 186
itself.
As can be seen from FIG. 30, the oscillator 181 is in contact with
the lower surface of the wafer W, and vibrates the wafer W in a
direction perpendicular to the surface of the wafer W. A frequency
and an amplitude of the vibration generated by the oscillator 181
can vary depending on a voltage applied to the piezoelectric
element 186. The frequencies and/or the amplitudes of the
vibrations generated by the oscillators 181 that are provided on
the chucks 45, respectively, may be the same as or different from
each other.
At least two of all oscillators 181 may vibrate at different
frequencies and/or different amplitudes. For example, a first group
consisting of three oscillators 181-1, 181-3, 181-5 shown in FIG.
32 may vibrate at frequency of tens of kHz to hundreds of kHz,
while a second group consisting of three oscillators 181-2, 181-4,
181-6, which are located between the oscillators belonging to the
first group, may vibrate at frequency of 1 MHz. The amplitude of
the vibration of the oscillators 181-1,181-3, 181-5 belonging to
the first group may be the same as or different from the amplitude
of the vibration of the oscillators 181-2, 181-4, 181-6 belonging
to the second group.
The wafer W is cleaned as follows. The wafer W is rotated about its
central axis by the substrate holder 41 and is vibrated by the
oscillators 181 at predetermined frequency and amplitude. In this
state, the two-fluid nozzle 42 delivers the two-fluid jet onto the
upper surface of the wafer W, while moving in the radial direction
of the wafer W. The upper surface of the wafer W is cleaned by a
combined action of the vibration applied by the oscillators 181 and
the impact of the two-fluid jet.
FIG. 33 is a schematic view showing a state in which the
oscillators 181 are vibrating the wafer W, and FIG. 34 is a
schematic view showing a state in which the two-fluid jet is
delivered onto the surface of the wafer W while the oscillators 181
are vibrating the wafer W. As shown in FIG. 33, when the vibration
is applied to the wafer W, the particles are likely to be separated
from the wafer W. In this state, the two-fluid jet is supplied onto
the wafer W, thereby removing the particles from the wafer W. In
this manner, a cleaning efficiency of the wafer W can be improved
by a combination of the vibration of the wafer W and the impact of
the two-fluid jet.
The oscillator 181 does not indirectly vibrate the wafer W through
the chuck 45, but directly vibrates the wafer W with its contact
surface 182 in contact with the wafer W. Therefore, the chuck 45
itself hardly vibrates, and thus the chuck 45 can stably hold the
wafer W. In other words, the oscillator 181 according to this
embodiment can vibrate only the wafer W without vibrating the chuck
45.
FIG. 35 is a view showing still another embodiment. In this
embodiment, the oscillator 181 is located so as to come in contact
with a circumferential surface (i.e., an outermost end surface) of
the wafer W, and to vibrate the wafer W in a direction parallel to
the surface of the wafer W. This oscillator 181 has a contact
surface 182 that is to come in contact with the circumferential
surface of the wafer W. The structure of the oscillator 181 is the
same as that of the oscillator 181 shown in FIG. 31, and repetitive
descriptions thereof are omitted. According to this embodiment, the
oscillator 181 vibrates the wafer W in the direction parallel to
the surface of the wafer W during cleaning of the wafer W with the
two-fluid jet.
FIG. 36 is a view showing still another embodiment. In this
embodiment, each one of chucks 45 is provided with two oscillators
181A, 181B. The first oscillator 181A has the same structure as
that of the oscillator 181 shown in FIG. 30, and is disposed at the
same location as that of the oscillator 181 shown in FIG. 30. More
specifically, the first oscillator 181A is in contact with the
lower surface of the peripheral of the wafer W to vibrate the wafer
W in the direction perpendicular to the surface of the wafer W. The
second oscillator 181B has the same structure as that of the
oscillator 181 shown in FIG. 35, and is disposed at the same
location as that of the oscillator 181 shown in FIG. 35. More
specifically, the second oscillator 181B is in contact with the
circumferential surface (i.e., the outermost end surface) of the
wafer W to vibrate the wafer W in the direction parallel to the
surface of the wafer W.
According to this embodiment, the second oscillator 181B vibrates
the wafer W in the direction parallel to the surface of the wafer
W, while the first oscillator 181A vibrates the wafer W in the
direction perpendicular to the surface of the wafer W. Therefore,
the particles are more likely to be separated from the wafer W. In
this state, the two-fluid jet is supplied onto the wafer W to
remove the particles from the wafer W. In this manner, the cleaning
efficiency of the wafer W can be further improved by a combination
of the vibration of the wafer W in two directions and the impact of
the two-fluid jet. A frequency and/or an amplitude of the vibration
of the first oscillator 181A may be the same as or may be different
from a frequency and/or an amplitude of the vibration of the second
oscillator 181B.
FIG. 37 is a view showing still another embodiment. Although not
shown in FIG. 37, each of the chucks 45 shown in FIG. 37 is
provided with the oscillator 181 shown in FIG. 30 and/or the
oscillator 181 shown in FIG. 35. Structures and operations of this
embodiment that are not described particularly are identical to
those of the embodiment shown in FIG. 29, and repetitive
descriptions thereof are omitted.
In this embodiment, a cleaning-liquid nozzle 190, which supplies a
cleaning liquid onto the lower surface of the wafer W, is disposed
below the wafer W held by the substrate holder 41. This
cleaning-liquid nozzle 190 is secured to an upper end of a
supporting shaft 195. A cleaning-liquid supply line 200 is coupled
to a lower end of the supporting shaft 195. A rotational shaft 201,
which couples the chucks 45 to the motor 48, is constituted by a
hollow shaft, and the supporting shaft 195 extends through the
rotational shaft 201. The rotational shaft 201 and the chucks 45
are rotated by the motor 48, while the supporting shaft 195 and the
cleaning-liquid nozzle 190 are not rotated.
A liquid-receiving cup 203, which has a cylindrical shape, is
provided around the wafer W held by the substrate holder 41. This
liquid-receiving cup 203 serves to receive the liquid that has been
supplied to the rotating wafer W and then direct the liquid
downwardly. This liquid-receiving cup 203 may be provided in the
substrate cleaning apparatus according to the above-described
embodiment shown in FIG. 29.
A passage 196 is formed in the supporting shaft 195. The
cleaning-liquid supply line 200 supplies the cleaning liquid into
the passage 196 of the supporting shaft 195. The cleaning-liquid
supply line 200 is provided with a cleaning-liquid supply source
206 and a gas-mixing device 207. The gas-mixing device 207 is a
device configured to mix a gas, such as nitrogen gas or hydrogen
gas, into the cleaning liquid supplied from the cleaning-liquid
supply source 206. The cleaning liquid containing such a dissolved
gas passes through the cleaning-liquid supply line 200 and the
passage 196 and is supplied to the cleaning-liquid nozzle 190. The
cleaning liquid may be pure water.
FIG. 38 is a plan view of the cleaning-liquid nozzle 190, FIG. 39
is a perspective view of the cleaning-liquid nozzle 190, and FIG.
40 is an enlarged cross-sectional view of the cleaning-liquid
nozzle 190. The cleaning-liquid nozzle 190 extends in a diametrical
direction of the wafer W. As shown in FIG. 40, the cleaning-liquid
nozzle 190 has a plurality of ejection mouths 211, and a plurality
of passages 212 which are in communication with these ejection
mouths 211, respectively. A plurality of ultrasonic transducers 215
are embedded in the cleaning-liquid nozzle 190, and are located so
as to come in contact with the cleaning liquid flowing in the
passages 212, respectively, to vibrate the cleaning liquid. The
cleaning liquid, to which the vibration energy has been
transmitted, passes through the plurality of passages 212 and is
then supplied from the ejection mouths 212 onto the lower surface
of the wafer W. A distance from the ejection mouths 211 to the
lower surface of the wafer W is preferably not more than 10 mm, and
more preferably not more than 5 mm.
Each of the ultrasonic transducers 215 is disposed below each of
the ejection mouths 211, and is configured to vibrate the cleaning
liquid immediately before the cleaning liquid is supplied onto the
wafer W. When the ultrasonic transducer 215 vibrates the cleaning
liquid, the gas that has been dissolved in the cleaning liquid
forms bubbles, which can improve the cleaning effect of the
cleaning liquid.
Cleaning of the wafer W is performed as follows. The wafer W is
rotated about its central axis by the substrate holder 41 and is
vibrated by the oscillators 181 at predetermined frequency and
amplitude. Further, the cleaning liquid is supplied onto the lower
surface of the wafer W while the cleaning liquid is vibrated by the
ultrasonic transducers 215. In this state, the two-fluid nozzle 42
supplies the two-fluid jet onto the upper surface of the wafer W,
while moving in the radial direction of the wafer W. The upper
surface of the wafer W is cleaned by the combined action of the
vibration applied by the oscillators 181 and the impact of the
two-fluid jet, while the lower surface of the wafer W is cleaned
with the cleaning liquid on which the vibration energy has been
exerted.
The ejection mouths 211 of the cleaning-liquid nozzle 190, which
are disposed below the lower surface of the wafer W, may be
arranged along a movement path of the two-fluid nozzle 42 that is
disposed above the upper surface of the wafer W. For example, as
shown in FIG. 41, the cleaning-liquid nozzle 190 may be in a shape
of a circular arc extending along an arcuate movement path of the
two-fluid nozzle 42.
In the embodiments shown in FIGS. 38 through 41, the two-fluid
nozzle 42 is used, while a pen sponge can be used instead of the
two-fluid nozzle 42.
The previous description of embodiments is provided to enable a
person skilled in the art to make and use the present invention.
Moreover, various modifications to these embodiments will be
readily apparent to those skilled in the art, and the generic
principles and specific examples defined herein may be applied to
other embodiments. Therefore, the present invention is not intended
to be limited to the embodiments described herein but is to be
accorded the widest scope as defined by limitation of the
claims.
* * * * *